The web inspector (aka. Dev tools) allows you to edit websites in real-time. It comes pre-installed with Google Chrome Browser — you already have it, just right-click and choose "inspect" and you're using it.
In this video I show you the basics of how to use the web inspector to edit the HTML (copy and images) and CSS (colors, font) on a website.
If you'd like to learn more about HTML vs. CSS
https://learn.onemonth.com/html-vs-css/
One Month HTML is my online course where you can learn both HTML & CSS in more depth. As well as 20-minute deep dive into using the web inspector. https://onemonth.com/courses/html